Mobile Computing and Its Applications

A technology that allows transmission of data, via a computer, without having to be connected to a fixed physical link. Mobile voice communication is widely established throughout the world and has had a very rapid increase in the number of subscribers to the various cellular networks over the last few years. An extension of this technology is the ability to send and receive data across these cellular networks. This is the principle of mobile computing.

Mobile Computing has fast become an important new paradigm in today's world of networked computing systems. Ranging from wireless laptops to cellular phones and WiFi/Bluetooth-enabled PDAs to wireless sensor networks, mobile computing has become ubiquitous in its impact on our daily lives. The debut if iPhones and the proliferation of other handheld devices have spurred excitement and interest in this evolving field. In this seminar, we will study the state-of-the-art in both the research and commercial communities with respect to mobile computing. We will investigate standard protocols and platforms, the capabilities of today's commercial devices, and proposed next-generation solutions. In the process, we will seek to gain an improved understanding about where the field is headed, and what is the importance of the mobile computing. Mobile computing is a fast-growing technology, a paper presentation on Mobile Computing explains in detail about this topic. Now a day’s cellular technology is the most widely used technology. It works on the frequencies that connect to millions of the users. The earlier analog technology was used that was based on the wires to connect but they are limited to the home. Then in 1990s GSM technology came that introduced the mobiles, and it becomes the mode of communication from anywhere and at any time. Every cell consists of a number of channels and they are needs to register to the nearest base stations. The Mobile Data Challenge was introduced when the amount of mobile data was seen to be increased very much in a short period of time. The rise of big data demands that this data can be accessed from everywhere and anytime. For handling such a huge amount of data e.g. SMS, images, videos etc, this data must be compressed for easy transmission over the network.

Mobile Computing is a technology that allows transmission of data, voice, and video via a computer or any other wireless-enabled device without having to be connected to a fixed physical link. This paper will give an overview of Mobile Computing and then it will take you through how it evolved and where is the technology headed to in the future along with the classifications and security issues involved.

Mobile telephony took off with the introduction of cellular technology which allowed the efficient utilization of frequencies enabling the connection of a large number of users. During the 1980's analog technology was used. Among the most well-known systems were the NMT900 and 450 (Nordic Mobile Telephone) and the AMPS (Advanced Mobile Phone Service). In the 1990's the digital cellular technology was introduced with GSM (Global System Mobile) being the most widely accepted system around the world. Other such systems are the DCS1800 (Digital Communication System) and the PCS1900 (Personal Communication System).

A cellular network consists of mobile units linked together to switching equipment, which interconnect the different parts of the network and allow access to the fixed Public Switched Telephone Network (PSTN). The technology is hidden from view; it's incorporated in a number of transceivers called Base Stations (BS). Every BS is located at a strategically selected place and covers a given area or cell - hence the name cellular communications. A number of adjacent cells grouped together form an area and the corresponding BSs communicate through a so-called Mobile Switching Centre (MSC). The MSC is the heart of a cellular radio system. It is responsible for routing, or switching calls from the originator to the destination. It can be thought of managing the cell, being responsible for set-up, routing control and termination of the call, for management of inter-MSC handover and supplementary services, and for collecting charging and accounting information. The MSC may be connected to other MSCs on the PSTN.

Mobile Switching Centre

The frequencies used vary according to the cellular network technology implemented. For GSM, 890 - 915 MHz range is used for transmission and 935 -960 MHz for the reception. The DCS technology uses frequencies in the 1800MHz range while PCS in the 1900MHz range.

Each cell has a number of channels associated with it. These are assigned to subscribers on demand. When a Mobile Station (MS) becomes 'active' it registers with the nearest BS. The corresponding MSC stores the information about that MS and its position. This information is used to direct incoming calls to the MS. If during a call the MS moves to an adjacent cell then a change of frequency will necessarily occur - since adjacent cells never use the same channels. This procedure is called hand over and is the key to Mobile communications. As the MS is approaching the edge of a cell, the BS monitors the decrease in signal power. The strength of the signal is compared with adjacent cells and the call is handed over to the cell with the strongest signal.

During the switch, the line is lost for about 400ms. When the MS is going from one area to another it registers itself to the new MSC. Its location information is updated, thus allowing MSs to be used outside their 'home' areas.

Data Communications is the exchange of data using existing communication networks. The term data covers a wide range of applications including File Transfer, the interconnection between Wide-Area-Networks, facsimile (fax), electronic mail, access to the internet and the World Wide Web.

Mobile Communications Overview

Data Communications have been achieved using a variety of networks such as PSTN, leased-lines and more recently ISDN (Integrated Services Data Network) and ATM (Asynchronous Transfer Mode)/Frame Relay. These networks are partly or totally analog or digital using technologies such as circuit - switching, packet - switching e.t.c.
Circuit switching implies that data from one user (sender) to another (receiver) has to follow a pre-specified path. If a link to be used is busy, the message cannot be redirected, a property which causes many delays.

Packet switching is an attempt to make better utilization of the existing network by splitting the message to be sent into packets. Each packet contains information about the sender, the receiver, the position of the packet in the message as well as part of the actual message.

The introduction of mobility in data communications required a move from the Public Switched Data Network to other networks like the ones used by mobile phones. PCSI has come up with an idea called CDPD technology which uses the existing mobile network. Mobility implemented in data communications has a significant difference compared to voice communications. Mobile phones allow the user to move around and talk at the same time; the loss of the connection for 400ms during the hand over is undetectable by the user. When it comes to data, 400ms is not only detectable but causes huge distortion to the message. Therefore data can be transmitted from a mobile station under the assumption that it remains stable or within the same cell.

CDPD Technology: The Hot Cookie

Today, the mobile data communications market is becoming dominated by a technology called CDPD. CDPD's principle lies in the usage of the idle time in between existing voice signals that are being sent across the cellular networks. The major advantage of this system is the fact that the idle time is not chargeable and so the cost of data transmission is very low. This may be regarded as the most important consideration by business individuals. There are other alternatives to this technology namely Circuit Switched Cellular, Specialised Mobile Radio and Wireless Data Networks. As can be seen from the table below the CDPD technology is much more advantageous than the others.

CDPD networks allow fixed or mobile users to connect to the network across a fixed link and a packet switched system respectively. Fixed users have a fixed physical link to the CDPD network. In the case of a mobile end user, the user can, if CDPD network facilities are non-existent, connect to existing circuit switched networks and transmit data via these networks. This is known as Circuit Switched CDPD (CS-CDPD).

Why Is CDPD Technology Better Than Circuit Switched?

CDPD is not better than Circuit Switch for transmitting data, but rather it is different. They both have their place in the cellular wireless solution, and it may take the combination of both services to provide the customer with the optimal solution. As stated above, the two technologies are different. CDPD is connection-less. It sends each packet intermittently when there is "space" available. Circuit Switching, on the other hand, sends the data over a continuous connection. For this reason, CDPD would be the optimal solution for a customer who is sending information which is both "short" and "bursty", the circuit switch solution would be optimal when sending a large data transmission. Another important difference is that CDPD uses less power than circuit switching. Since the information is sent in short bursts, the device only has to be at high levels of power for short intervals. Additionally, CDPD has a "sleep" mode which allows the device to conserve power when not in use, without logging off of the network. Therefore, a mobile computing device will have longer battery life using the CDPD technology rather than circuit switched connections. Lastly, CDPD uses an encryption technique to prevent an outside source from receiving the transmitted data.

The hierarchy consists of the following levels:

• Mobile Data Base Station (MDBS).

In each cell of the cellular reception area, there is a Mobile Data Base Station (MDBS) which is responsible for detection of idle time in voice channels, for relaying data between the mobile units and the Mobile Data Intermediate Systems (MDIS), sending of packets of data onto the appropriate unoccupied frequencies as well as receiving data packets and passing them to the appropriate Mobile end user within its domain.

• Detection of idle time.

This is achieved using a scanning receiver(also known as a sniffer) housed in the MDBS. The sniffer detects voice traffic by measuring the signal strength on a specific frequency, hence detecting an idle channel. When the situation occurs that all voice channels are at capacity, then extra frequencies specifically set aside for CDPD data can be utilized. Although this scenario is unlikely as each cell within the reception area typically 57 channels, each of which has an average of 25 - 30% of the idle time.

Groups of MDBS that control each cell in the cellular network reception area are connected to a higher level entity in the network hierarchy, the Mobile Data Intermediate Systems. The connection is made via a wideband trunk cable. These MDIS use a Mobile Network Location Protocol (MNLP) to exchange location information about Mobile end users within their domain. In the reverse direction, where messages are from the Mobile end user, packets are routed directly to their destination and not necessarily through the mobile end users home MDIS.

MDIS are interconnected to these IS which form the backbone of the CDPD system. These systems are unaware of the mobility of end-users, as this is hidden by lower levels of the network hierarchy. The ISs are the systems that provide the CDPD interface to the various computer and phone networks.

CDPD Network.There are some actions that are necessary in order to obtain reliability over a network.

User Authentication. The procedure which checks if the identity of the subscriber transferred over the radio path corresponds with the details held in the network.

Fraud Prevention. Protection against impersonation of authorized users and fraudulent use of the network is required.

User Anonymity. Instead of the actual directory telephone number, the International Mobile Subscriber Identity (IMSI) number is used within the network to uniquely identify a mobile subscriber.

Protection of user data. All the signals within the network are encrypted and the identification key is never transmitted through the air. This ensures maximum network and data security.

With the rapid technological advancements in Artificial Intelligence, Integrated Circuitry and increases in Computer Processor speeds, the future of mobile computing looks increasingly exciting. Use of Artificial Intelligence may allow mobile units to be the ultimate in personal secretaries, which can receive emails and paging messages, understand what they are about, and change the individual's personal schedule according to the message.